An amphibious craft is salvaged from the Delaware River in Philadelphia Friday after it was knocked over by an oncoming barge Wednesday, spilling 37 people overboard and killing two.

PHILADELPHIA (AP)  Friends silently and solemnly dropped white roses into the Delaware River on Saturday in memory of the two Hungarian students who died when the amphibious tourist boat they were riding was struck by a barge and sank.

City officials, religious leaders and Hungarian diplomats joined the group of grieving Hungarian exchange students at a memorial service dedicated to 20-year-old Szabolcs Prem and 16-year-old Dora Schwendtner, who drowned after the duck boat capsized Wednesday.

"The loss of a young life, of two young lives, is almost impossible to understand and almost impossible to accept," said Bela Szombati, the Hungarian ambassador to the United States. "We stand with you, we stand with the children, the young people."

At the end of the ceremony, wreaths and flowers were dropped into the river and a pair of doves were released.

Both bodies were recovered from the river Friday and identified based on their personal effects, said Jeff Moran, spokesman for the Philadelphia medical examiner's office.

The two crewmembers and 33 other passengers on the duck boat were rescued from the river. Eleven of the survivors were Hungarian students. Two Hungarian teachers and seven Americans who were touring with them also survived.

The National Transportation Safety Board sent a team of 10 investigators to Philadelphia to piece together how the crash occurred. They say the duck boat's captain shut off the engine and dropped its anchor after smoke billowed from the vessel. The boat was stopped in the water for five to 10 minutes before the barge, being pushed by a tugboat, struck it. It capsized within seconds.

Among the issues to sort out: whether the tugboat crew heard distress calls that the duck boat crew says it made, and why an air horn on the smaller vessel apparently failed.

The NTSB, which said it would have no more briefings on its investigation, was conducting interviews Saturday with the five crewmembers of the tugboat.

Saturday, though, was a day of remembrance, with clergy offering prayers in English and the Hungarian language of Magyar.

Philadelphia Mayor Michael Nutter apologized to the survivors on behalf of his city.

John Oostdyk, the director of the exchange program Atlantic Bridge, described the two victims as full of potential.

He said in an interview after the memorial service at the Independence Seaport Museum that he had gotten to know Prem over the past few years.

He described him as a shy young man a year out of high school who was emerging as a leader in the exchange program.

"He was just a growing up kid," said Oostdyk, who flew to Philadelphia from the Netherlands after he heard about the crash. "He didn't know what he was going to do" for a career.

Szombati, the Hungarian ambassador, traveled from Washington to offer his support to the students.

"Unfortunately, it has changed the world of these young people," he said.

Szombati said the embassy was working at logistical details such as replacing the passports that were lost in the river and arranging for the students, who were one week into a three-week visit to the U.S., to go home early.

The students who attended the memorial did not speak with the media.

Several hundred people attended a candlelight vigil held Saturday night at the victims' high school in the northwestern Hungarian city of Mosonmagyarovar, state news wire MTI reported.

Karoly Hansagi, principal of the Lajos Kossuth Gymnasium, gave a speech in remembrance of the victims, expressing astonishment, pain and anger over the young lives that were lost.

Later, mourners placed flowers by the students' photographs, displayed on a school wall.

Meanwhile, Ride the Ducks, the Norcross, Ga.-based company that owns the duck boat, said it was resuming operations in Atlanta, San Francisco and Branson, Mo., and expected to resume rides soon in Newport, Ky. Boats in Philadelphia remained out of service.

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